JP2015007706A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of eliminating electrical charges on a recording sheet and reducing deterioration of image quality.SOLUTION: The image forming apparatus comprises: a photoreceptor drum 27; a transfer roller 30 forming a nip part N with the photoreceptor drum 27; and a first static eliminating member 110 and a second static eliminating member 120 configured to eliminate electrical charges on the recording sheet having passed the nip part N. At least a part of the first static eliminating member 110 is disposed in a printing area in a width direction of the recording sheet. The second static eliminating member 120 is disposed only in a non-printing area in the width direction and is disposed at a position closer to the nip part N than the first static eliminating member 110 in a conveyance direction of the recording sheet.

Description

  The present invention relates to an image forming apparatus including a charge removal member for removing a charge on a recording sheet that has passed through a nip formed by a photosensitive drum and a transfer roller.

  Conventionally, an electrophotographic image forming apparatus is configured to transfer a developer image on a photosensitive drum to the recording sheet by sandwiching the recording sheet between the photosensitive drum and a transfer roller to which a transfer bias is applied. There is something. In such an image forming apparatus, the conveyed recording sheet is charged when it passes through the nip formed by the photosensitive drum and the transfer roller. For example, in the image forming apparatus of Patent Document 1, the recording sheet passes through the nip. A neutralizing member for neutralizing the recorded sheet is provided.

  Specifically, the static elimination member is provided at the exit of the nip portion, and is configured to face the surface on the transfer roller side of the recording sheet that has passed through the nip portion, and to remove the charge charged on the recording sheet. Yes. As a result, the conveyance of the recording sheet that has passed through the nip portion can be stabilized, and paper jams and image disturbances can be suppressed.

JP 2001-154494 A

  By the way, when the leading edge of the recording sheet that has passed through the nip portion is warped, the leading edge of the recording sheet may be greatly separated from the charge removal member, and the recording sheet may not be sufficiently discharged. Therefore, it is desirable to dispose the charge removal member at a position close to the nip portion where the distance from the recording sheet is short.

  However, if the static elimination member is brought close to the nip portion, a part of the transfer current may flow (leakage) to the static elimination member via the recording sheet passing through the nip portion. As described above, when the transfer current leaks, an appropriate transfer current cannot be obtained, so that the image quality is deteriorated.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of removing the charge on a recording sheet and reducing image quality degradation.

In order to achieve the above-described object, the image forming apparatus of the present invention is configured to remove the charge on the photosensitive drum, the transfer roller that forms the nip portion with the photosensitive drum, and the recording sheet that has passed through the nip portion. A first charge removal member and a second charge removal member configured.
At least a part of the first charge removal member is disposed in the print region in the width direction of the recording sheet.
The second static elimination member is arranged only outside the printing area in the width direction, and is arranged at a position closer to the nip portion than the first static elimination member in the recording sheet conveyance direction.

  According to the image forming apparatus configured as described above, the second charge eliminating member is disposed close to the nip portion, so that even if the leading edge of the recording sheet is warped, the charge on the recording sheet is reliably removed. can do. Further, since only the second static elimination member provided outside the printing area is disposed at a position close to the nip portion, even if the transfer current leaks to the second static elimination member via the recording sheet, the amount of leakage Is less than when leaking to both the first static elimination member and the second static elimination member. Thereby, it is possible to minimize the deterioration of the image quality due to the leakage of the transfer current.

  In the image forming apparatus described above, the first static elimination member extends perpendicularly to a first straight line passing through the rotation axis of the photosensitive drum and the rotation axis of the transfer roller when viewed from the axial direction of the photosensitive drum, and the nip portion The second static elimination member crosses the second straight line when viewed from the axial direction of the photosensitive drum, or is separated from the second straight line, and the tip and the second straight line are separated from each other. It is desirable that the distance is shorter than the distance between the tip of the first static elimination member and the second straight line.

  According to the image forming apparatus configured as described above, the recording sheet can be neutralized more effectively by the second neutralizing member. Moreover, since the 1st static elimination member provided in the printing area | region does not contact a recording sheet, it can reduce that a leak arises.

  In the above-described image forming apparatus, the first charge removal member may be a brush including a plurality of bristles arranged in the width direction of the recording sheet and having a conductive surface.

  The above-described second static elimination member may be a brush including a plurality of bristles lined up in the width direction of the recording sheet and having a conductive surface.

  In this case, the second static elimination member described above extends perpendicularly to the first straight line passing through the rotation axis of the photosensitive drum and the rotation axis of the transfer roller, as viewed from the axial direction of the photosensitive drum, and the second straight line passing through the nip portion. It is desirable to cross.

  According to the image forming apparatus configured as described above, the recording sheet is surely brought into contact with the second static elimination member. However, since the second static elimination member is a brush, the recording sheet falls when the recording sheet comes into contact. It is possible to suppress the conveyance.

  According to the present invention, even when the leading edge of the recording sheet is warped, the charge on the recording sheet can be surely removed and the deterioration of the image quality can be minimized.

1 is a diagram illustrating a schematic configuration of a laser printer according to an embodiment of the present invention. It is sectional drawing which shows the structure of the periphery of a static elimination member. It is a perspective view which shows a static elimination member and a metal plate. It is sectional drawing which shows the structure of the periphery of the static elimination member in a modification.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the overall configuration of a laser printer as an example of an image forming apparatus will be briefly described, and then details of the characteristic portions of the present invention will be described.

  Further, in the following description, the description will be made in the direction based on the user when the laser printer 1 is used. That is, in FIG. 1, the right side is referred to as “front side”, the left side is referred to as “rear side”, the back side in the vertical direction of the paper is referred to as “right side”, and the front side in the vertical direction of the paper surface is referred to as “left side”. Called. As for the vertical direction, the vertical direction in the figure is referred to as the “vertical direction” as it is.

<Overall configuration of laser printer>
As shown in FIG. 1, a laser printer 1 includes a feeder unit 4 for feeding a sheet 3 as an example of a recording sheet in an apparatus main body 2, an image forming unit 5 for forming an image on the sheet 3, and the like. It has.

  The feeder unit 4 has a known structure, and mainly includes a paper feed tray 6, a paper pressing plate 7, and a paper transport mechanism 9. In the feeder unit 4, the paper 3 in the paper feed tray 6 is brought close to the paper transport mechanism 9 provided above by the paper pressing plate 7 and is transported to the image forming unit 5 by the paper transport mechanism 9.

  The image forming unit 5 includes a scanner unit 16, a process cartridge 17, a paper guide 18, a fixing device 19, and the like.

  The scanner unit 16 includes a laser light emitting unit, a polygon mirror, a lens, a reflecting mirror, and the like (not shown). In the scanner unit 16, the laser beam is irradiated on the surface of the photosensitive drum 27 by high-speed scanning through a path indicated by a chain line in the drawing.

  The process cartridge 17 can be attached to and detached from the apparatus main body 2 by appropriately opening the front cover 2A on the front side of the apparatus main body 2. The process cartridge 17 is mainly composed of a developing cartridge 28 and a drum unit 51.

  The developing cartridge 28 is detachably attached to the apparatus main body 2 via the drum unit 51 or is detachably attached to the drum unit 51 fixed to the apparatus main body 2. The developing cartridge 28 mainly includes a developing roller 31, a layer thickness regulating blade 32, a supply roller 33, and a toner hopper 34.

  In the developing cartridge 28, the toner accommodated in the toner hopper 34 is stirred by the agitator 34 </ b> A and then supplied to the developing roller 31 by the supply roller 33. At this time, between the supply roller 33 and the developing roller 31. Positively triboelectrically charged. The toner supplied onto the developing roller 31 enters between the layer thickness regulating blade 32 and the developing roller 31 as the developing roller 31 rotates, and is further developed as a thin layer having a constant thickness while being frictionally charged. It is carried on a roller 31.

  The drum unit 51 mainly includes a known photosensitive drum 27, a scorotron charger 29 and a transfer roller 30. The transfer roller 30 is disposed below the photosensitive drum 27 and is provided so as to form a nip portion N (see FIG. 2) with the photosensitive drum 27. A transfer bias is applied to the transfer roller 30 by constant current control during transfer.

  In the drum unit 51, the surface of the photosensitive drum 27 is uniformly positively charged by the scorotron charger 29 and then exposed by high-speed scanning of the laser beam from the scanner unit 16. Thereby, the potential of the exposed part is lowered, and an electrostatic latent image based on the image data is formed.

  Next, by the rotation of the developing roller 31, the toner carried on the developing roller 31 is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 27, so that the toner image is formed on the surface of the photosensitive drum 27. It is formed. Thereafter, the sheet 3 passes between the photosensitive drum 27 and the transfer roller 30 (nip portion N), whereby the toner image carried on the surface of the photosensitive drum 27 is transferred onto the sheet 3.

  The paper guide 18 is disposed behind the drum unit 51, and the upper surface 18 </ b> A is opposed to the lower surface of the paper 3 to be conveyed, and is configured to guide the paper 3 that has passed through the nip portion N toward the fixing device 19. . The sheet guide 18 is provided with a charge removal member 100 configured to remove the electric charge on the sheet 3 that has passed through the nip N at the front end. As a result, the sheet 3 is neutralized on the upstream side in the conveyance direction with respect to the sheet guide 18, so that the sheet 3 can be stably conveyed by the sheet guide 18. The configuration of the charge removal member 100 will be described in detail later.

  The fixing device 19 has a known structure and includes a heating roller 41 and a pressing roller 42. In the fixing device 19, the toner transferred onto the paper 3 is thermally fixed while the paper 3 passes between the heating roller 41 and the pressing roller 42. The paper 3 thermally fixed by the fixing unit 19 is sent out onto the paper discharge tray 46 by the paper discharge roller 45.

<Detailed configuration of static elimination member>
Next, the configuration of the charge removal member 100 will be described in detail.

  As shown in FIG. 2, the charge removal member 100 is provided in the vicinity of the exit of the nip portion N formed by the photosensitive drum 27 and the transfer roller 30. The static elimination member 100 includes a first static elimination member 110 disposed downstream of the nip portion N and upstream of the paper guide 18 in the conveyance direction of the paper 3 (from front to rear), and the first static elimination member. And a second static elimination member 120 disposed closer to the nip portion N than 110.

  The first static elimination member 110 and the second static elimination member 120 are respectively fixed to the metal plate 200 provided at the front end of the paper guide 18 and protrude upward from the upper surface 18A of the paper guide 18.

  Here, the metal plate 200 is a sheet metal placed on the upper surface 18A of the paper guide 18. The metal plate 200 includes a main body 201 mounted on the upper surface 18 </ b> A of the paper guide 18, a first extension 210 that extends downward from the front end of the main body 201, and a front of the first extension 210 from the front end of the main body 201. And a second extension part 220 extending downward. The metal plate 200 is grounded by a ground member (not shown).

  As shown in FIG. 3, the first extending portion 210 includes a print area in the width direction (left-right direction) of the paper 3 and is provided slightly wider than the print area. The second extending portion 220 is provided on both sides in the left-right direction of the first extending portion 210, and is provided outside the print area in the width direction of the paper 3.

  The static elimination member 100 is formed as one component, and the first static elimination member 110 and the second static elimination member 120 are integrated.

  The neutralizing member 100 is a brush including a plurality of hairs 101 arranged in the width direction (left-right direction) of the paper 3 and an adhesive tape 102 for fixing the plurality of hairs 101 to the metal plate 200.

  The adhesive tape 102 is, for example, an aluminum tape and has conductivity. The adhesive tape 102 includes a first portion 102A that constitutes the first static elimination member 110, a second portion 102B that is disposed on both sides in the left-right direction of the first portion 102A, and that constitutes the second static elimination member 120, and each first portion 102A. A third portion 102C that connects an end portion on the outer side in the left-right direction and an end portion on the inner side in the left-right direction of the second portion 102B. The first portion 102 </ b> A extends in the left-right direction longer than the width of the print area of the paper 3.

  The hair 101 of the static elimination member 100 is, for example, a fiber whose surface is covered with metal, and the surface has conductivity. The hair 101 of the static elimination member 100 includes a first hair 101A provided in the first portion 102A and a second hair 101B provided in the second portion 102B. The second hair 101B is a first hair. It is longer than 101A.

  The neutralizing member 100 configured as described above is fixed to the metal plate 200 by being attached along the shape of the front end portion of the metal plate 200.

  Specifically, in the static elimination member 100, the first portion 102A of the adhesive tape 102 is attached to the front surface of the first extension portion 210, and the second portion 102B of the adhesive tape 102 is attached to the front surface of the second extension portion 220. It is attached.

  Thereby, the both ends of the 1st static elimination member 110 are arrange | positioned in the horizontal direction outer side rather than the printing area | region of the paper 3, and the 1st hair | bristle 101A of the 1st static elimination member 110 is in the width direction of the paper 3. The printing area is provided from the outside of one end to the outside of the other end. The second static elimination member 120 is disposed only outside the print area in the width direction of the paper 3.

  As shown in FIG. 2, the tip of the second hair 101 </ b> B of the second charge removal member 120 is located above the tip of the first hair 101 </ b> A of the first charge removal member 110.

  Specifically, the first bristles 101A of the first static elimination member 110 are seen from the axial direction (left-right direction) of the photosensitive drum 27, and the common tangent L1 (first) between the photosensitive drum 27 and the transfer roller 30 in the nip portion N. 2 straight lines). The second bristles 101 </ b> B of the second static elimination member 120 intersect the common tangent line L <b> 1 between the photosensitive drum 27 and the transfer roller 30 in the nip portion N as viewed from the axial direction of the photosensitive drum 27. The common tangent line L1 is a straight line that extends perpendicularly to a straight line (first straight line) that passes through the rotation axis of the photosensitive drum 27 and the rotation axis of the transfer roller 30 and passes through the nip portion N.

The operation and effect of the laser printer 1 configured as described above will be described.
The sheet 3 fed from the feeder unit 4 passes through a nip N formed by the photosensitive drum 27 and the transfer roller 30. The leading edge of the sheet 3 that has passed through the nip portion N is first neutralized by the second neutralizing member 120 that is disposed closer to the nip portion N than the first neutralizing member 110.

  In the present embodiment, the second bristles 101B of the second static elimination member 120 intersect the common tangent L1 between the photosensitive drum 27 and the transfer roller 30 at the nip portion N as viewed from the axial direction of the photosensitive drum 27. The leading edge of the sheet 3 that has passed through the nip portion N reliably contacts the second bristles 101B of the second static elimination member 120. Thereby, the sheet 3 can be reliably discharged by the second discharging member 120.

  When the leading edge of the paper 3 is warped, the leading edge of the paper 3 moves away from the common tangent line L1 as it goes downstream from the nip portion N in the transport direction, but the second static elimination member 120 It is disposed at a position closer to the nip portion N than the member 110, and at this position, the leading edge of the sheet 3 is not greatly separated from the common tangent line L1. Thereby, even if the leading edge of the paper 3 is warped, the second static elimination member 120 can surely eliminate the static charge.

  Even if the sheet 3 contacts the second static elimination member 120 as described above, the contacted portion is the second bristles 101B and can fall down when contacted. Must not.

  Since the second static elimination member 120 is provided only outside the print area in the width direction of the paper 3, the range where the second hair 101B of the second static elimination member 120 and the paper 3 are in contact with each other is Compared to the case where the member contacts the entire width direction of the sheet 3, it is narrower. As a result, even if the transfer current flows to the charge removal member 100 via the paper 3, the amount of the transfer current is small, so that deterioration in image quality due to a decrease in the transfer current can be reduced.

  When the leading edge of the sheet 3 reaches the position where the first charge removal member 110 is provided, the sheet 3 is also discharged by the first charge removal member 110.

  In the present embodiment, the first bristles 101A of the first static elimination member 110 are separated from the common tangent L1 between the photosensitive drum 27 and the transfer roller 30 in the nip portion N when viewed from the axial direction of the photosensitive drum 27. The first hair 101 </ b> A of the first static elimination member 110 does not come into contact with the conveyed paper 3. That is, since the static eliminating member 100 does not contact within the print area of the paper 3, it is possible to suppress the developer image on the paper 3 from being disturbed. In addition, since the transfer current does not flow to the first static elimination member 110 that is not in contact with the paper 3, it is possible to suppress deterioration in image quality.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention.

  In the embodiment, the second static elimination member 120 intersects the common tangent L1 of the photosensitive drum 27 and the transfer roller 30 in the nip portion N when viewed from the axial direction of the photosensitive drum 27. However, the present invention is not limited to this. Is not to be done. For example, as shown in FIG. 4, the second static elimination member 120 is separated from the common tangent L1 of the photosensitive drum 27 and the transfer roller 30 in the nip portion N when viewed from the axial direction of the photosensitive drum 27, and is connected to the tip and the common tangent L1. May be provided to be closer than the distance between the tip of the first static elimination member 110 and the common tangent L1.

  Even when the second static elimination member 120 is provided in this way, the paper 3 that has passed through the nip portion N when the leading edge of the paper 3 is warped, compared to the case where the static elimination member is provided only at the position of the first static elimination member 110. Since the distance between the second neutralization member 120 and the second neutralization member 120 is reduced, the sheet 3 can be sufficiently neutralized.

  In the embodiment, the first static elimination member 110 and the second static elimination member 120 have a plurality of bristles 101A and 101B arranged in the width direction of the paper 3 (the width direction with respect to the conveyance direction of the paper 3). However, the present invention is not limited to this. For example, the first static elimination member 110 and the second static elimination member 120 may have a plurality of metal needles arranged in the width direction of the paper 3. In this case, the metal needle does not intersect the common tangent L1 between the photosensitive drum 27 and the transfer roller 30 at the nip portion N when viewed from the axial direction of the photosensitive drum 27 in order not to disturb the conveyance of the sheet 3. It is desirable to provide as follows.

DESCRIPTION OF SYMBOLS 1 Laser printer 3 Paper 27 Photosensitive drum 30 Transfer roller 100 Static elimination member 110 1st static elimination member 120 2nd static elimination member 200 Metal plate L1 Common tangent N Nip part

Claims (5)

A photosensitive drum;
A transfer roller that forms a nip with the photosensitive drum;
A first static elimination member and a second static elimination member configured to remove electric charges on the recording sheet that has passed through the nip portion,
The first static elimination member is at least partially disposed in the print area in the width direction of the recording sheet,
The second charge eliminating member is disposed only outside the printing area in the width direction, and is disposed closer to the nip portion than the first charge eliminating member in the recording sheet conveyance direction. Image forming apparatus. The first static elimination member extends perpendicularly to a first straight line passing through the rotation axis of the photosensitive drum and the rotation axis of the transfer roller when viewed from the axial direction of the photosensitive drum, and from a second straight line passing through the nip portion. Apart,
The second static elimination member intersects the second straight line when viewed from the axial direction of the photosensitive drum or is separated from the second straight line, and the distance between the tip and the second straight line is the first straight line. The image forming apparatus according to claim 1, wherein the distance is shorter than a distance between a tip of the charge removal member and the second straight line.   3. The image forming apparatus according to claim 1, wherein the first charge eliminating member is a brush including a plurality of bristles arranged in the width direction of the recording sheet and having a conductive surface.   4. The brush according to claim 1, wherein the second static elimination member is a brush including a plurality of bristles arranged in a width direction of the recording sheet and having a conductive surface. Image forming apparatus.   The second static elimination member extends perpendicularly to a first straight line passing through the rotational axis of the photosensitive drum and the rotational axis of the transfer roller, as viewed from the axial direction of the photosensitive drum, and a second straight line passing through the nip portion. The image forming apparatus according to claim 4, wherein the image forming apparatuses cross each other.

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